Phase-change material (PCM) RF switch having contacts to PCM and heating element

ABSTRACT

In fabricating a radio frequency (RF) switch, a phase-change material (PCM) and a heating element, underlying an active segment of the PCM and extending outward and transverse to the PCM, are provided. Lower portions of PCM contacts for connection to passive segments of the PCM are formed, wherein the passive segments extend outward and are transverse to the heating element. Upper portions of the PCM contacts are formed from a lower interconnect metal. Heating element contacts are formed cross-wise to the PCM contacts. The heating element contacts can comprise a top interconnect metal directly connecting with terminal segments of the heating element. The heating element contacts can comprise a top interconnect metal and intermediate metal segments for connecting with the terminal segments of the heating element.

CLAIMS OF PRIORITY

This is a divisional of application Ser. No. 16/114,106 filed on Aug.27, 2018. Application Ser. No. 16/114,106 filed on Aug. 27, 2018 (“theparent application”) is a continuation-in-part of and claims the benefitof and priority to application Ser. No. 16/103,490 filed on Aug. 14,2018, titled “Manufacturing RF Switch Based on Phase-Change Material.”The parent application is also a continuation-in-part of and claims thebenefit of and priority to application Ser. No. 16/103,587 filed on Aug.14, 2018, titled “Design for High Reliability RF Switch Based onPhase-Change Material.” The parent application is further acontinuation-in-part of and claims the benefit of and priority toapplication Ser. No. 16/103,646 filed on Aug. 14, 2018, titled “PCM RFSwitch Fabrication with Subtractively Formed Heater.” The disclosuresand contents of all of the above-identified applications are herebyincorporated fully by reference into the parent application and thepresent divisional application.

BACKGROUND

Phase-change materials (PCM) are capable of transforming from acrystalline phase to an amorphous phase. These two solid phases exhibitdifferences in electrical properties, and semiconductor devices canadvantageously exploit these differences. Given the ever-increasingreliance on radio frequency (RF) communication, there is particular needfor RF switching devices to exploit phase-change materials. However, thecapability of phase-change materials for phase transformation dependsheavily on how they are exposed to thermal energy and how they areallowed to release thermal energy. For example, in order to transforminto an amorphous state, phase-change materials may need to achievetemperatures of approximately seven hundred degrees Celsius (700° C.) ormore, and may need to cool down within hundreds of nanoseconds.

Heating elements in PCM RF switches and contacts to the heating elementsoften create tradeoffs with parasitics associated with RF frequenciesand result in performance tradeoffs. Additionally, the performance of anRF switch using PCM depends heavily on how contacts to the PCM are made.Fabricating contacts to both PCM and to heating elements withoutsignificant RF performance tradeoffs becomes complex, especially wherethe RF switch is designed primarily around thermal performance.Accordingly, accommodating PCM in RF switches can present significantmanufacturing challenges. Specialty manufacturing is often impractical,and large scale manufacturing generally trades practicality for theability to control device characteristics and critical dimensions.

Thus, there is a need in the art to simply and reliably manufacture lowparasitics PCM RF switches.

SUMMARY

The present disclosure is directed to fabrication of contacts andinterconnect metallization in an RF switch having a phase-changematerial (PCM) and a heating element, substantially as shown in and/ordescribed in connection with at least one of the figures, and as setforth in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B each illustrate a portion of a flowchart of an exemplarymethod for manufacturing contacts and interconnect metallization in aphase-change material (PCM) RF switch according to one implementation ofthe present application.

FIG. 2A illustrates a top view of a portion of a PCM RF switch structureprocessed in accordance with an action in the flowchart of FIG. 2Aaccording to one implementation of the present application.

FIGS. 2B and 2C each illustrate a cross-sectional view of a portion of aPCM RF switch structure processed in accordance with an action in theflowchart of FIG. 1A according to one implementation of the presentapplication.

FIG. 3A illustrates a top view of a portion of a PCM RF switch structureprocessed in accordance with an action in the flowchart of FIG. 1Aaccording to one implementation of the present application.

FIGS. 3B and 3C each illustrate a cross-sectional view of a portion of aPCM RF switch structure processed in accordance with an action in theflowchart of FIG. 1A according to one implementation of the presentapplication.

FIG. 4A illustrates a top view of a portion of a PCM RF switch structureprocessed in accordance with an action in the flowchart of FIG. 1Aaccording to one implementation of the present application.

FIGS. 4B and 4C each illustrate a cross-sectional view of a portion of aPCM RF switch structure processed in accordance with an action in theflowchart of FIG. 1A according to one implementation of the presentapplication.

FIG. 5A illustrates a top view of a portion of a PCM RF switch structureprocessed in accordance with an action in the flowchart of FIG. 1Aaccording to one implementation of the present application.

FIGS. 5B and 5C each illustrate a cross-sectional view of a portion of aPCM RF switch structure processed in accordance with an action in theflowchart of FIG. 1A according to one implementation of the presentapplication.

FIG. 6A illustrates a top view of a portion of a PCM RF switch structureprocessed in accordance with an action in the flowchart of FIG. 1Aaccording to one implementation of the present application.

FIGS. 6B and 6C each illustrate a cross-sectional view of a portion of aPCM RF switch structure processed in accordance with an action in theflowchart of FIG. 1A according to one implementation of the presentapplication.

FIG. 7A illustrates a top view of a portion of a PCM RF switch structureprocessed in accordance with an action in the flowchart of FIG. 1Baccording to one implementation of the present application.

FIGS. 7B and 7C each illustrate a cross-sectional view of a portion of aPCM RF switch structure processed in accordance with an action in theflowchart of FIG. 1B according to one implementation of the presentapplication.

FIG. 8A illustrates a top view of a portion of a PCM RF switch structureprocessed in accordance with an action in the flowchart of FIG. 1Baccording to one implementation of the present application.

FIGS. 8B and 8C each illustrate a cross-sectional view of a portion of aPCM RF switch structure processed in accordance with an action in theflowchart of FIG. 1B according to one implementation of the presentapplication.

FIG. 9A illustrates a top view of a portion of a PCM RF switch structureprocessed in accordance with an action in the flowchart of FIG. 1Baccording to one implementation of the present application.

FIGS. 9B and 9C each illustrate a cross-sectional view of a portion of aPCM RF switch structure processed in accordance with an action in theflowchart of FIG. 1B according to one implementation of the presentapplication.

FIG. 10A illustrates a top view of a portion of a PCM RF switchstructure processed in accordance with an action in the flowchart ofFIG. 1B according to one implementation of the present application.

FIGS. 10B and 10C each illustrate a cross-sectional view of a portion ofa PCM RF switch structure processed in accordance with an action in theflowchart of FIG. 1B according to one implementation of the presentapplication.

FIG. 11A illustrates a top view of a portion of a PCM RF switchstructure processed in accordance with an action in the flowchart ofFIG. 1A according to one implementation of the present application.

FIGS. 11B and 11C each illustrate a cross-sectional view of a portion ofa PCM RF switch structure processed in accordance with an action in theflowchart of FIG. 1A according to one implementation of the presentapplication.

FIG. 12A illustrates a top view of a portion of a PCM RF switchstructure processed in accordance with an action in the flowchart ofFIG. 1A according to one implementation of the present application.

FIGS. 12B and 12C each illustrate a cross-sectional view of a portion ofa PCM RF switch structure processed in accordance with an action in theflowchart of FIG. 1A according to one implementation of the presentapplication.

FIG. 13A illustrates a top view of a portion of a PCM RF switchstructure processed in accordance with an action in the flowchart ofFIG. 1A according to one implementation of the present application.

FIGS. 13B and 13C each illustrate a cross-sectional view of a portion ofa PCM RF switch structure processed in accordance with an action in theflowchart of FIG. 1A according to one implementation of the presentapplication.

FIG. 14A illustrates a top view of a portion of a PCM RF switchstructure processed in accordance with an action in the flowchart ofFIG. 1A according to one implementation of the present application.

FIGS. 14B and 14C each illustrate a cross-sectional view of a portion ofa PCM RF switch structure processed in accordance with an action in theflowchart of FIG. 1A according to one implementation of the presentapplication.

FIG. 15 illustrates a cross-sectional view of a portion of an PCM RFswitch structure according to one implementation of the presentapplication.

DETAILED DESCRIPTION

The following description contains specific information pertaining toimplementations in the present disclosure. The drawings in the presentapplication and their accompanying detailed description are directed tomerely exemplary implementations. Unless noted otherwise, like orcorresponding elements among the figures may be indicated by like orcorresponding reference numerals. Moreover, the drawings andillustrations in the present application are generally not to scale, andare not intended to correspond to actual relative dimensions.

FIG. 1A illustrates a portion of a flowchart of an exemplary method formanufacturing contacts and interconnect metallization in a phase-changematerial (PCM) RF switch according to one implementation of the presentapplication. Certain details and features have been left out of theflowchart that are apparent to a person of ordinary skill in the art.For example, an action may consist of one or more subactions or mayinvolve specialized equipment or materials, as known in the art.Moreover, some actions, such as masking and cleaning actions, areomitted so as not to distract from the illustrated actions. Actions 112through 120 and actions 130 through 136 shown in flowchart 100A of FIG.1A, together with actions 122 through 128 in flowchart 100B of FIG. 1B,are sufficient to describe exemplary implementations of the presentinventive concepts, other implementations of the present inventiveconcepts may utilize actions different from those shown in flowcharts100A and 100B. Moreover, structures shown in FIGS. 2A through 14Cillustrate the results of performing actions 112 through 136.

By way of overview and referring to flowcharts 100A and 100B, thepresent exemplary implementation begins with action 112 by providing aPCM and a heating element underlying an active segment of the PCM. Theexemplary implementations continue with action 114 by etching holes in acontact dielectric overlying passive segments of the PCM, and then withaction 116 by forming lower portions of PCM contacts for connection tothe passive segments of the PCM. From action 116, one implementation cancontinue with action 118, or an alternative implementation can continuewith action 130. As described below, where the method continues withaction 118, upper portions of PCM contacts will have an offset towardsthe active segment of the PCM. Where the method continues with action130, and upper portions of PCM contacts will have an offset away fromthe active segment of the PCM.

Addressing the implementation having upper portions of PCM contacts withan offset towards the active segment of the PCM, action 118 includesforming upper portions of the PCM contacts from a lower interconnectmetal. From action 118, the method continues with action 120 bydepositing a layer of an interconnect dielectric. From action 120, themethod continues with and concludes with actions 122 through 128.

Addressing the alternative implementation having upper portions of PCMcontacts with an offset away from the active segment of the PCM, action130 includes planarizing the lower portions of the PCM contacts with thecontact dielectric. From action 130, the method continues with action132 by depositing a layer of a lower interconnect metal. The methodcontinues with action 134 by forming upper portions of the PCM contactsfrom the lower interconnect metal. The method concludes with action 136by completing contacts by remaining manufacturing actions.

FIGS. 2A through 6C and illustrate the results of performing actions 112through 120 of flowchart 100A of FIG. 1A, according to oneimplementation of the present disclosure. For example, structures 212A,212B, and 212C, show a PCM RF switch structure after performing action112, structures 314A, 314B, and 314C show a PCM RF switch structureafter performing action 114, and so forth.

Referring to FIG. 2A, PCM RF switch structure 212A illustrates a topview of a portion of a PCM RF switch structure processed in accordancewith action 112 in flowchart 100A of FIG. 1A according to oneimplementation of the present application. As shown in FIG. 2A, PCM RFswitch structure 212A includes substrate 240, heat spreader 242, heatingelement 246 having terminal segments 248, and PCM 254 having activesegment 256 and passive segments 258. For purposes of illustration, thetop view in FIG. 2A shows selected structures of PCM RF switch structure212A. PCM RF switch structure 212A may include other structures notshown in FIG. 2A.

Heat spreader 242 overlies substrate 240. Heat spreader 242 alsounderlies heating element 246. Heat spreader 242 generally dissipatesexcess heat generated by PCM RF switch structure 212A. In particular,heat spreader 242 dissipates excess heat generated by heating element246 after a heat pulse, such as a crystallizing pulse or an amorphizingpulse, has transformed the state of PCM 254. Heat spreader 242 may beany material with high thermal conductivity. In one implementation, heatspreader 242 may be a material with both high thermal conductivity andhigh electrical resistivity. In various implementations, heat spreader242 can comprise aluminum nitride (AlN), aluminum oxide (Al_(X)O_(Y)),beryllium oxide (Be_(X)O_(Y)), silicon carbide (SiC), diamond, ordiamond-like carbon. In one implementation, heat spreader 242 includesstrain-relieving chamfers (not shown) at its sides and/or at itscorners. In one implementation, substrate 240 is an insulator, such assilicon oxide (SiO₂). In various implementations, substrate 240 is asilicon (Si), silicon-on-insulator (SOI), sapphire, complementarymetal-oxide-semiconductor (CMOS), bipolar CMOS (BiCMOS), or group III-Vsubstrate. In one implementation, heat spreader 242 itself performs as asubstrate and a separate substrate is not used. For example, heatspreader 242 can comprise Si and be provided without substrate 240. Inone implementation, heat spreader 242 can be integrated with substrate240. It is noted that in FIG. 2A, the top area of substrate 240 isgreater than that of heat spreader 242. However, in some implementationsheat spreader 242 can be coextensive with substrate 240.

Heating element 246 overlies heat spreader 242. Heating element 246 alsounderlies PCM 254. Heating element 246 in PCM RF switch structure 212Agenerates a crystallizing pulse or an amorphizing pulse for transformingactive region 256 of PCM 254. Heating element 246 can comprise anymaterial capable of Joule heating that has a melting temperature higherthan that of PCM 254. Preferably, heating element 246 comprises amaterial that exhibits little or substantially no electromigration. Invarious implementations, heating element 246 can comprise tungsten (W),molybdenum (Mo), titanium (Ti), titanium nitride (TiN), titaniumtungsten (TiW), tantalum (Ta), nickel chromium (NiCr), or nickelchromium silicon (NiCrSi).

PCM 254 overlies heating element 246. PCM 254 includes active segment256 and passive segments 258. As used herein, “active segment” refers toa segment of PCM that transforms between crystalline and amorphousstates, for example, in response to a crystallizing or an amorphizingheat pulse, whereas “passive segment” refers to a segment of PCM thatdoes not make such transformation and maintains a crystalline state(i.e., maintains a conductive state). PCM 254 can be germanium telluride(Ge_(X)Te_(Y)), germanium antimony telluride (Ge_(X)Sb_(Y)Te_(Z)),germanium selenide (Ge_(X)Se_(Y)), or any other chalcogenide. It isnoted that in FIG. 2A, heating element 246 extends outwards and istransverse to PCM 254. Current flowing in heating element 246 flowssubstantially under active segment 256 of PCM 254. In variousimplementations, PCM 254 can be germanium telluride having from fortypercent to sixty percent germanium by composition (i.e., Ge_(X)Te_(Y),where 0.4≤X≤0.6 andY=1−X). The material for PCM 254 can be chosen basedupon ON state resistivity, OFF state electric field breakdown threshold,crystallization temperature, melting temperature, or otherconsiderations.

Referring to FIG. 2B, PCM RF switch structure 212B illustrates across-sectional view of a portion of a PCM RF switch structure processedin accordance with action 112 in flowchart 100A of FIG. 1A according toone implementation of the present application. FIG. 2B represents across-sectional view along line “B-B” in FIG. 2A. As shown in FIG. 2B,PCM RF switch structure 212B includes substrate 240, heat spreader 242,lower dielectric 244, heating element 246, nugget 250, combined layer252, PCM 254 having active segment 256 and passive segments 258, andcontact dielectric 260. Substrate 240, heat spreader 242, heatingelement 246, and PCM 254 in FIG. 2B may have any implementations andadvantages described above.

Referring to FIG. 2B, lower dielectric 244 is situated over heatspreader 242, which is in turn situated over substrate 240. In oneimplementation, lower dielectric 244 is SiO₂. In other implementations,lower dielectric 244 is silicon nitride (Si_(X)N_(Y)), or anotherdielectric. In one implementation, lower dielectric 244 is also situatedunder heating element 246.

In PCM RF switch structure 212B, nugget 250 is situated on top ofheating element 246 and under active segment 256 of PCM 254. As usedherein “nugget” refers to a segment of thermally conductive andelectrically insulating material on top of heating element 246. Nugget250 ensures efficient heat transfer between heating element 246 andactive segment 256 of PCM 254, while preventing electrical signals fromleaking out from the path between PCM contacts to heating element 246 orto other neighboring structures. Nugget 250 can comprise any materialwith high thermal conductivity and high electrical resistivity. Invarious implementations, nugget 250 can comprise AlN, Al_(X)O_(Y),Be_(X)O_(Y), SiC, Si_(X)N_(Y), diamond, or diamond-like carbon. In theimplementation illustrated in FIG. 3A, nugget 250 is shown to comprisethe same material as heat spreader 242. However, in otherimplementations, nugget 250 and heat spreader 242 can comprise differentmaterials. In one implementation, nugget 250 can have a higher thermalconductivity than heat spreader 242 to ensure that a heat pulsegenerated by heating element 246 dissipates toward active segment 256 ofPCM 254 more rapidly than it dissipates toward heat spreader 242.

As shown in FIG. 2B, PCM RF switch structure 212B can optionally includecombined layer 252. Combined layer 252 includes segments situated on thesides of PCM 254 and over PCM 254. The segments of combined layer 252situated on the sides of PCM 254 may be referred to as a passivationlayer in the present application. The segment of combined layer 252situated over PCM 254 includes a passivation layer and a contactuniformity support layer which is situated on and is in direct contactwith PCM 254. The contact uniformity support layer assists duringformation of holes for lower portions of PCM contacts, as describedbelow. In various implementations, segments of combined layer 252 cancomprise silicon nitride (Si_(X)N_(Y)) or an oxide, such as SiO₂. InFIG. 2B, contact dielectric 260 is situated over combined layer 252 (incase combined layer 252 is utilized) and over PCM 254 and firstdielectric 244. In one implementation, contact dielectric 260 is SiO₂.In other implementations, contact dielectric 260 is Si_(X)N_(Y), oranother dielectric.

Referring to FIG. 2C, PCM RF switch structure 212C illustrates across-sectional view of a portion of a PCM RF switch structure processedin accordance with action 112 in flowchart 100A of FIG. 1A according toone implementation of the present application. FIG. 2C represents across-sectional view along line “C-C” in FIG. 2A. As shown in FIG. 2C,PCM RF switch structure 212C includes substrate 240, heat spreader 242,lower dielectric 244 that is situated over and around heating element246, combined layer 252, and contact dielectric 260. Substrate 240, heatspreader 242, lower dielectric 244, heating element 246, combined layer252, and contact dielectric 260 in FIG. 2C may have any implementationsand advantages described above. Notably, the cross-sectional view of PCMRF switch structure 212C in FIG. 2C does not include PCM 254, becauseline “C-C” in FIG. 2A lies along terminal segment 248 of heating element246, which extends outward and is transverse to PCM 254.

Referring to FIG. 3A, PCM RF switch structure 314A illustrates a topview of a portion of a PCM RF switch structure processed in accordancewith action 114 in flowchart 100A of FIG. 1A according to oneimplementation of the present application. As shown in FIG. 3A, PCM RFswitch structure 314A includes substrate 340, heat spreader 342, heatingelement 346 having terminal segments 348, PCM 354 having active segment356 and passive segments 358, and holes 362. For purposes ofillustration, the top view in FIG. 3A shows selected structures of PCMRF switch structure 314A. PCM RF switch structure 314A may include otherstructures not shown in FIG. 3A. Notably, in FIG. 3A, holes 362 (shownwith dashed lines) are etched in contact dielectric 360 (shown in FIG.3B) overlying passive segments 358 of PCM 354.

Referring to FIG. 3B, PCM RF switch structure 314B illustrates across-sectional view of a portion of a PCM RF switch structure processedin accordance with action 114 in flowchart 100A of FIG. 1A according toone implementation of the present application. FIG. 3B represents across-sectional view along line “B-B” in FIG. 3A. As shown in FIG. 3B,PCM RF switch structure 314B includes substrate 340, heat spreader 342,lower dielectric 344, heating element 346, nugget 350, combined layer352, PCM 354 having active segment 356 and passive segments 358, contactdielectric 360, and holes 362. Substrate 340, heat spreader 342, lowerdielectric 344, heating element 346, nugget 350, combined layer 352, PCM354 having active segment 356 and passive segments 358, and contactdielectric 360 in FIG. 3B may have any implementations and advantagesdescribed above.

As shown in FIG. 3B, holes 362 are etched through contact dielectric 360partially into passive segments 358 of PCM 354. Holes 362 are alsoetched through contact uniformity support layer of combined layer 352(in case combined layer 352 is used). In this implementation, action 114for etching holes in contact dielectric 360 overlying passive segments358 of PCM 354 may comprise two different etching actions. In the firstetching action, contact dielectric 360 can be aggressively etched toform most of holes 362. This first etching action can use a selectiveetch, for example, a fluorine-based plasma dry etch, and contactuniformity support layer of combined layer 352 can perform as an etchstop while contact dielectric 360 is selectively etched. In the secondetching action, contact uniformity support layer of combined layer 352can be etched less aggressively. As a result, PCM 354 will remainsubstantially intact, and uniform contact can be made to PCM 354.Because the R_(ON) of an RF switch depends heavily on the uniformity ofcontacts made with PCM 354, the R_(ON) will be significantly lower whencontact uniformity support layer of combined layer 352 is used. In oneimplementation, contact uniformity support layer of combined layer 352is substantially thinner than contact dielectric 360.

Referring to FIG. 3C, PCM RF switch structure 314C illustrates across-sectional view of a portion of a PCM RF switch structure processedin accordance with action 114 in flowchart 100A of FIG. 1A according toone implementation of the present application. FIG. 3C represents across-sectional view along line “C-C” in FIG. 3A. As shown in FIG. 3C,PCM RF switch structure 314C includes substrate 340, heat spreader 342,lower dielectric 344, heating element 346, combined layer 352, andcontact dielectric 360. Substrate 340, heat spreader 342, lowerdielectric 344, heating element 346, combined layer 352, and contactdielectric 360 in FIG. 3C may have any implementations and advantagesdescribed above. Notably, the cross-sectional view of PCM RF switchstructure 314C in FIG. 3C does not include PCM 354 or holes 362, becauseline “C-C” in FIG. 3A lies along terminal segment 348 of heating element346, which extends outward and is transverse to PCM 354.

Referring to FIG. 4A, PCM RF switch structure 416A illustrates a topview of a portion of a PCM RF switch structure processed in accordancewith action 116 in flowchart 100A of FIG. 1A according to oneimplementation of the present application. As shown in FIG. 4A, PCM RFswitch structure 416A includes lower interconnect metal 464. Forpurposes of illustration, the top view in FIG. 4A shows selectedstructures of PCM RF switch structure 416A. PCM RF switch structure 416Amay include other structures not shown in FIG. 4A. Notably, in FIG. 4A,lower interconnect metal 464 is situated atop PCM RF switch structure416A and in holes 362 (shown in FIG. 3B).

Referring to FIG. 4B, PCM RF switch structure 416B illustrates across-sectional view of a portion of a PCM RF switch structure processedin accordance with action 116 in flowchart 100A of FIG. 1A according toone implementation of the present application. FIG. 4B represents across-sectional view along line “B-B” in FIG. 4A. As shown in FIG. 4B,PCM RF switch structure 416B includes substrate 440, heat spreader 442,lower dielectric 444, heating element 446, nugget 450, combined layer452, PCM 454 having active segment 456 and passive segments 458, contactdielectric 460, and lower interconnect metal 464 having lower portions466. Substrate 440, heat spreader 442, lower dielectric 444, heatingelement 446, nugget 450, combined layer 452, PCM 454 having activesegment 456 and passive segments 458, and contact dielectric 460 in FIG.4B may have any implementations and advantages described above.

As shown in FIG. 4B, lower interconnect metal 464 is deposited in holes362 (shown in FIG. 3B) and over contact dielectric 460. Within holes 362(shown in FIG. 3B), lower interconnect metal 464 forms lower portions466 of PCM contacts connected to passive segments 458 of PCM 454. Invarious implementations, lower interconnect metal 464 can comprisetungsten (W), copper (Cu), or aluminum (Al). In one implementation, thetop surface of lower interconnect metal 464 can have indents in thevicinity of lower portions 466 of PCM contacts.

Referring to FIG. 4C, PCM RF switch structure 416C illustrates across-sectional view of a portion of a PCM RF switch structure processedin accordance with action 116 in flowchart 100A of FIG. 1A according toone implementation of the present application. FIG. 4C represents across-sectional view along line “C-C” in FIG. 4A. As shown in FIG. 4C,PCM RF switch structure 416C includes substrate 440, heat spreader 442,lower dielectric 444, heating element 446, combined layer 452, PCM 454having active segment 456 and passive segments 458, contact dielectric460, and lower interconnect metal 464. Substrate 440, heat spreader 442,lower dielectric 444, heating element 446, combined layer 452, PCM 454having active segment 456 and passive segments 458, contact dielectric460, and lower interconnect metal 464 in FIG. 4C may have anyimplementations and advantages described above. Notably, thecross-sectional view of PCM RF switch structure 416C in FIG. 4C does notinclude lower portions 466 of PCM contacts, because line “C-C” in FIG.4A lies along terminal a segment of heating element 446, which extendsoutward and is transverse to PCM 454.

Referring to FIG. 5A, PCM RF switch structure 518A illustrates a topview of a portion of a PCM RF switch structure processed in accordancewith action 118 in flowchart 100A of FIG. 1A according to oneimplementation of the present application. As shown in FIG. 5A, PCM RFswitch structure 518A includes substrate 540, heat spreader 542, heatingelement 546 having terminal segments 548, PCM 554 having active segment556, and PCM contacts 574 having upper portions 570. For purposes ofillustration, the top view in FIG. 5A shows selected structures of PCMRF switch structure 518A. PCM RF switch structure 518A may include otherstructures not shown in FIG. 5A. Notably, in Figure SA, upper portions570 of PCM contacts 574 are formed from lower interconnect metal 464(shown in FIG. 4A).

Referring to FIG. 5B, PCM RF switch structure 518B illustrates across-sectional view of a portion of a PCM RF switch structure processedin accordance with action 118 in flowchart 100A of FIG. 1A according toone implementation of the present application. FIG. 5B represents across-sectional view along line “B-B” in Figure SA. As shown in FigureSB, PCM RF switch structure 518B includes substrate 540, heat spreader542, lower dielectric 544, heating element 546, nugget 550, combinedlayer 552, PCM 554 having active segment 556 and passive segments 558,contact dielectric 560, and PCM contacts 574 having lower portions 566and upper portions 570. Substrate 540, heat spreader 542, lowerdielectric 544, heating element 546, nugget 550, combined layer 552, PCM554 having active segment 556 and passive segments 558, and contactdielectric 560 in FIG. 5B may have any implementations and advantagesdescribed above.

As shown in FIG. 5B, lower interconnect metal 464 (shown in FIG. 4B) hasbeen patterned, thereby forming upper portions 570 of PCM contacts 574.Further, as shown in FIG. 5B, upper portions 570 of PCM contacts 574have offsets 572 towards active segment 556 of PCM 554. Because formingupper portions 570 of PCM contacts 574 shown in FIG. 5B uses a singlemetal deposition and a single metal etch, manufacturing is simplified.However, where a single metal deposition is used, patterning upperportions 570 of PCM contacts 574 directly aligned with lower portions566 of PCM contacts 574 presents manufacturing difficulty. Inparticular, lower interconnect metal 464 (shown in FIG. 4B) can haveindents in the vicinity of lower portions 566 of PCM contacts 574, andthe manufacturing techniques used to pattern lower interconnect metal464 (shown in FIG. 4B) can exhibit alignment variations, which canresult in upper portions 570 of PCM contacts 574 being misaligned, andthus, the R_(ON) of an RF switch being higher than desired. Offsets 572towards active segment 556 of PCM 554 protect against these variationsand keep R_(ON) low.

Referring to FIG. 5C, PCM RF switch structure 518C illustrates across-sectional view of a portion of a PCM RF switch structure processedin accordance with action 118 in flowchart 100A of FIG. 1A according toone implementation of the present application. FIG. 5C represents across-sectional view along line “C-C” in FIG. 5A. As shown in FIG. 5C,PCM RF switch structure 518C includes substrate 540, heat spreader 542,lower dielectric 544, heating element 546, combined layer 552, andcontact dielectric 560. Substrate 540, heat spreader 542, lowerdielectric 544, heating element 546, combined layer 552, and contactdielectric 560 in FIG. 5C may have any implementations and advantagesdescribed above. Notably, the cross-sectional view of PCM RF switchstructure 518C in FIG. 5C does not include PCM contacts 574, becauseline “C-C” in FIG. 5A lies along terminal segment 548 of heating element546, which extends outward and is transverse to PCM 554.

Referring to FIG. 6A, PCM RF switch structure 620A illustrates a topview of a portion of a PCM RF switch structure processed in accordancewith action 120 in flowchart 100A of FIG. 1A according to oneimplementation of the present application. As shown in FIG. 6A, PCM RFswitch structure 620A includes substrate 640, heat spreader 642, heatingelement 646 having terminal segments 648, PCM 654 having active segment656, and PCM contacts 674 having upper portions 670. For purposes ofillustration, the top view in FIG. 6A shows selected structures of PCMRF switch structure 620A. PCM RF switch structure 620A may include otherstructures not shown in FIG. 6A. Notably, in FIG. 6A, a layer ofinterconnect dielectric 676 (shown in FIG. 6B) has been deposited.

Referring to FIG. 6B, PCM RF switch structure 620B illustrates across-sectional view of a portion of a PCM RF switch structure processedin accordance with action 120 in flowchart 100A of FIG. 1A according toone implementation of the present application. FIG. 6B represents across-sectional view along line “B-B” in FIG. 6A. As shown in FIG. 6B,PCM RF switch structure 620B includes substrate 640, heat spreader 642,lower dielectric 644, heating element 646, nugget 650, combined layer652, PCM 654 having active segment 656 and passive segments 658, contactdielectric 660, PCM contacts 674 having lower portions 666 and upperportions 670, and interconnect dielectric 676. Substrate 640, heatspreader 642, lower dielectric 644, heating element 646, nugget 650,combined layer 652, PCM 654 having active segment 656 and passivesegments 658, contact dielectric 660, and PCM contacts 674 having lowerportions 666 and upper portions 670 in FIG. 6B may have anyimplementations and advantages described above.

As shown in FIG. 68, a layer of interconnect dielectric 676 is depositedover PCM contacts 674 and over contact dielectric 660, and thenplanarized. In one implementation, contact dielectric 660 is SiO₂. Inother implementations, contact dielectric 660 is Si_(X)N_(Y), or anotherdielectric.

Referring to FIG. 6C, PCM RF switch structure 620C illustrates across-sectional view of a portion of a PCM RF switch structure processedin accordance with action 120 in flowchart 100A of FIG. 1A according toone implementation of the present application. FIG. 6C represents across-sectional view along line “C-C” in FIG. 6A. As shown in FIG. 6C,PCM RF switch structure 620C includes substrate 640, heat spreader 642,lower dielectric 644, heating element 646, combined layer 652, contactdielectric 660, and interconnect dielectric 676. Substrate 640, heatspreader 642, lower dielectric 644, heating element 646, combined layer652, contact dielectric 660, and interconnect dielectric 676 in FIG. 6Cmay have any implementations and advantages described above. Notably,the cross-sectional view of PCM RF switch structure 620C in FIG. 6C doesnot include PCM contacts 674, because line “C-C” in FIG. 6A lies alongterminal segment 648 of heating element 646, which extends outward andis transverse to PCM 654.

FIG. 1B illustrates the remaining portion of the flowchart of Figure Aillustrating an exemplary method for manufacturing contacts in a PCM RFswitch according to one implementation of the present application.Certain details and features have been left out of the flowchart thatare apparent to a person of ordinary skill in the art. For example, anaction may consist of one or more subactions or may involve specializedequipment or materials, as known in the art. Moreover, some actions,such as masking and cleaning actions, are omitted so as not to distractfrom the illustrated actions. Actions 122 through 128 shown in flowchart100B of FIG. 1B are sufficient to describe one implementation of thepresent inventive concepts, other implementations of the presentinventive concepts may utilize actions different from those shown inflowchart 100B of FIG. 1B. Moreover, structures shown in FIGS. 7Athrough 10C illustrate the results of performing actions 122 through 128in flowchart 100B of FIG. 1B.

By way of overview, and as illustrated in FIG. 1B, flowchart 100Bcontinues with action 122 by etching holes in the interconnectdielectric overlying the upper portions of the PCM contacts. The methodcontinues with action 124 by etching holes in the interconnectdielectric and the contact dielectric overlying terminal segments of theheating element. In one implementation, action 124 can be performedprior to action 122. The method continues with action 126 by depositinga top interconnect metal directly connecting with the terminal segmentsof the heating element. The method concludes with action 128 by formingheating element contacts “cross-wise” to the PCM contacts.

FIGS. 7A through 10C and illustrate the results of performing actions122 through 128 of flowchart 100B of FIG. 1B, according to oneimplementation of the present disclosure. For example, structures 722A,722B, and 722C, show a PCM RF switch structure after performing action122, structures 824A, 824B, and 824C show a PCM RF switch structureafter performing action 124, and so forth.

Referring to FIG. 7A, PCM RF switch structure 722A illustrates a topview of a portion of a PCM RF switch structure processed in accordancewith action 122 in flowchart 100B of FIG. 1B according to oneimplementation of the present application. As shown in FIG. 2B, PCM RFswitch structure 722A includes substrate 740, heat spreader 742, heatingelement 746 having terminal segments 748, PCM 754 having active segment756, PCM contacts 774 having upper portions 770, and holes 778. Forpurposes of illustration, the top view in FIG. 7A shows selectedstructures of PCM RF switch structure 722A. PCM RF switch structure 722Amay include other structures not shown in FIG. 7A. Notably, in FIG. 7A,holes 778 (shown with dashed lines) are etched in interconnectdielectric 776 (shown in FIG. 7B) overlying upper portions 770 of PCMcontacts 774.

Referring to FIG. 7B, PCM RF switch structure 722B illustrates across-sectional view of a portion of a PCM RF switch structure processedin accordance with action 122 in flowchart 100B of FIG. 1B according toone implementation of the present application. FIG. 7B represents across-sectional view along line “B-B” in FIG. 7A. As shown in FIG. 7B,PCM RF switch structure 722B includes substrate 740, heat spreader 742,lower dielectric 744, heating element 746, nugget 750, combined layer752, PCM 754 having active segment 756 and passive segments 758, contactdielectric 760, PCM contacts 774 having lower portions 766 and upperportions 770, interconnect dielectric 776, and holes 778. Substrate 740,heat spreader 742, lower dielectric 744, heating element 746, nugget750, combined layer 752, PCM 754 having active segment 756 and passivesegments 758, contact dielectric 760, PCM contacts 774 having lowerportions 766 and upper portions 770, and interconnect dielectric 776 inFIG. 7B may have any implementations and advantages described above.

As shown in FIG. 7B, holes 778 are etched through and interconnectdielectric 776 to upper portions 770 of PCM contacts 774. Notably, holes778 are etched overlying terminal segments of upper portions 770 of PCMcontacts 774, away from active segment 756 of PCM 754.

Referring to FIG. 7C, PCM RF switch structure 722C illustrates across-sectional view of a portion of a PCM RF switch structure processedin accordance with action 122 in flowchart 100B of FIG. 1B according toone implementation of the present application. FIG. 7C represents across-sectional view along line “C-C” in FIG. 7A. As shown in FIG. 7C,PCM RF switch structure 722C includes substrate 740, heat spreader 742,lower dielectric 744, heating element 746, combined layer 752, contactdielectric 760, and interconnect dielectric 776. Substrate 740, heatspreader 742, lower dielectric 744, heating element 746, combined layer752, contact dielectric 760, and interconnect dielectric 776 in FIG. 7Cmay have any implementations and advantages described above. Notably,the cross-sectional view of PCM RF switch structure 722C in FIG. 7C doesnot include holes 778 in interconnect dielectric 776 overlying upperportions 770 of PCM contacts 774, because line “C-C” in FIG. 7A liesalong terminal segment 748 of heating element 746, which extends outwardand is transverse to PCM 754, and also because analogous holes have notbeen etched in interconnect dielectric 776 overlying terminal segments748 of heating element 746. As shown in FIG. 7A, holes are etchedoverlying upper portions 770 of PCM contacts 774, but not overlyingterminal segments 748 of heating element 746.

Referring to FIG. 8A, PCM RF switch structure 824A illustrates a topview of a portion of a PCM RF switch structure processed in accordancewith action 124 in flowchart 100B of FIG. 1B according to oneimplementation of the present application. As shown in FIG. 8A, PCM RFswitch structure 824A includes substrate 840, heat spreader 842, heatingelement 846 having terminal segments 848, PCM 854 having active segment856, PCM contacts 874 having upper portions 870, holes 878, and holes880. For purposes of illustration, the top view in FIG. 8A showsselected structures of PCM RF switch structure 824A. PCM RF switchstructure 824A may include other structures not shown in FIG. 8A.Notably, in FIG. 8A, holes 880 (shown with dashed lines) are etched ininterconnect dielectric 876 (shown in FIG. 8C), contact dielectric 860(shown in FIG. 8C), combined layer 852 (in case combined layer 852 isused; shown in FIG. 8C), and lower dielectric 844 (shown in FIG. 8C)overlying terminal segments 848 of heating element 846.

Referring to FIG. 8B, PCM RF switch structure 824B illustrates across-sectional view of a portion of a PCM RF switch structure processedin accordance with action 124 in flowchart 100B of FIG. 1B according toone implementation of the present application. FIG. 8B represents across-sectional view along line “B-B” in FIG. 8A. As shown in FIG. 8B,PCM RF switch structure 824B includes substrate 840, heat spreader 842,lower dielectric 844, heating element 846, nugget 850, combined layer852, PCM 854 having active segment 856 and passive segments 858, contactdielectric 860, PCM contacts 874 having lower portions 866 and upperportions 870, interconnect dielectric 876, and holes 878. Substrate 840,heat spreader 842, lower dielectric 844, heating element 846, nugget850, combined layer 852, PCM 854 having active segment 856 and passivesegments 858, contact dielectric 860, PCM contacts 874 having lowerportions 866 and upper portions 870, interconnect dielectric 876, andholes 878 in FIG. 8B may have any implementations and advantagesdescribed above. Notably, the cross-sectional view of PCM RF switchstructure 824B in FIG. 8B does not include holes 880 (shown in FIG. 8C)in interconnect dielectric 876 and in contact dielectric 860 overlyingterminal segments of heating element 846, because line “B-B” in FIG. 8Alies along PCM 854. As shown in FIG. 8A, holes 880 are etched overlyingterminal segments 848 of heating element 846, whereas holes 878 areseparately etched overlying terminal segments of upper portions 870 ofPCM contacts 874.

Referring to FIG. 8C, PCM RF switch structure 824C illustrates across-sectional view of a portion of a PCM RF switch structure processedin accordance with action 124 in flowchart 100B of FIG. 1B according toone implementation of the present application. FIG. 8C represents across-sectional view along line “C-C” in FIG. 8A. As shown in FIG. 8C,PCM RF switch structure 824C includes substrate 840, heat spreader 842,lower dielectric 844, heating element 846, combined layer 852, contactdielectric 860, interconnect dielectric 876, and hole 880. Substrate840, heat spreader 842, lower dielectric 844, heating element 846,combined layer 852, contact dielectric 860, and interconnect dielectric876 in FIG. 8C may have any implementations and advantages describedabove.

As shown in FIG. 8C, hole 880 is etched through and interconnectdielectric 876, contact dielectric 860, and combined layer 852 (in casecombined layer 852 is used), and partially through lower dielectric 844,to heating element 846. In this implementation, action 124 for etchinghole 880 in interconnect dielectric 876 and contact dielectric 860overlying terminal segments of heating element 846 may comprise twodifferent etching actions. In the first etching action, interconnectdielectric 876, and contact dielectric 860 can be etched to form most ofhole 880. This first etching action can use a selective etch, forexample, a fluorine-based plasma dry etch, and combined layer 852 (incase combined layer 852 is used) can perform as an etch stop whileinterconnect dielectric 876 and contact dielectric 860 are selectivelyetched. The second etching action can use a selective etch, for example,a chlorine-based plasma dry etch, and heating element 846 can perform asan etch stop while combined layer 852 (in case combined layer 852 isused) and lower dielectric 844 are selectively etched.

As a result, heating element 846 will remain substantially intact, anduniform contact can be made to heating element 846. Notably, holes 878(shown in FIG. 8B) and hole 880 (shown in FIG. 8C) did not etch throughinterconnect dielectric 876 in the same action. Additionally, hole 880etched through contact dielectric 860, combined layer 852 (in casecombined layer 852 is used), and lower dielectric 844. Thus, holes 878(shown in FIG. 8B) and hole 880 (shown in FIG. 8C) have differentdepths. Holes 878 (shown in FIG. 8B) reach to upper portions 870 of PCMcontacts 874, while hole 880 (shown in FIG. 8C) reaches to heatingelement 846, which underlies active segment 856 of PCM 854 and extendsoutward and is transverse to PCM 854. In one implementation, holes 878have depths of approximately five thousands angstroms (5000 Å), and hole880 has a depth of approximately two microns (2 μm). In oneimplementation holes 878 (shown in FIG. 8B) and hole 880 (shown in FIG.8C) can be etched concurrently, rather than separately.

Referring to FIG. 9A, PCM RF switch structure 926A illustrates a topview of a portion of a PCM RF switch structure processed in accordancewith action 126 in flowchart 100B of FIG. 1B according to oneimplementation of the present application. As shown in FIG. 9A, PCM RFswitch structure 926A includes top interconnect metal 982. For purposesof illustration, the top view in FIG. 9A shows selected structures ofPCM RF switch structure 926A. PCM RF switch structure 926A may includeother structures not shown in FIG. 9A. Notably, in FIG. 9A, topinterconnect metal 982 is situated atop PCM RF switch structure 926A, inholes 878 (shown in FIG. 8A), and in holes 880 (shown in FIG. 8A).

Referring to FIG. 9B, PCM RF switch structure 926B illustrates across-sectional view of a portion of a PCM RF switch structure processedin accordance with action 126 in flowchart 100B of FIG. 1B according toone implementation of the present application. FIG. 9B represents across-sectional view along line “B-B” in FIG. 9A. As shown in FIG. 9B,PCM RF switch structure 926B includes substrate 940, heat spreader 942,lower dielectric 944, heating element 946, nugget 950, combined layer952, PCM 954 having active segment 956 and passive segments 958, contactdielectric 960, PCM contacts 974 having lower portions 966 and upperportions 970, interconnect dielectric 976, and top interconnect metal982. Substrate 940, heat spreader 942, lower dielectric 944, heatingelement 946, nugget 950, combined layer 952, PCM 954 having activesegment 956 and passive segments 958, contact dielectric 960, PCMcontacts 974 having lower portions 966 and upper portions 970, andinterconnect dielectric 976 in FIG. 9B may have any implementations andadvantages described above.

As shown in FIG. 9B, top interconnect metal 982 is deposited in holes878 (shown in FIG. 8B) and over interconnect dielectric 976. Topinterconnect metal 982 is connected to upper portions 970 and forms atop interconnect of PCM contacts 974. In various implementations, topinterconnect metal 982 can comprise W, Cu, or Al. In one implementation,the top surface of top interconnect metal 982 can have indents in thevicinity of in holes 878 (shown in FIG. 8B).

Referring to FIG. 9C, PCM RF switch structure 926C illustrates across-sectional view of a portion of a PCM RF switch structure processedin accordance with action 126 in flowchart 100B of FIG. 1B according toone implementation of the present application. FIG. 9C represents across-sectional view along line “C-C” in FIG. 9A. As shown in FIG. 9C,PCM RF switch structure 926C includes substrate 940, heat spreader 942,lower dielectric 944, heating element 946, combined layer 952, contactdielectric 960, interconnect dielectric 976, and top interconnect metal982. Substrate 940, heat spreader 942, lower dielectric 944, heatingelement 946, combined layer 952, contact dielectric 960, andinterconnect dielectric 976 in FIG. 9C may have any implementations andadvantages described above.

As shown in FIG. 9C, top interconnect metal 982 is deposited in holes880 (shown in FIG. 8C) and over interconnect dielectric 976. Topinterconnect metal 982 is connected to terminal segments of heatingelement 946. In one implementation, the top surface of top interconnectmetal 982 can have indents in the vicinity of in hole 880 (shown in FIG.8C).

Referring to FIG. 10A, PCM RF switch structure 1028A illustrates a topview of a portion of a PCM RF switch structure processed in accordancewith action 128 in flowchart 100B of FIG. 1B according to oneimplementation of the present application. As shown in FIG. 10A, PCM RFswitch structure 1028A includes substrate 1040, heat spreader 1042,heating element 1046, PCM 1054 having active segment 1056, PCM contacts1074 having upper portions 1070 and top interconnects 1083, and heatingelement contacts 1086. For purposes of illustration, the top view inFIG. 10A shows selected structures of PCM RF switch structure 1028A. PCMRF switch structure 1028A may include other structures not shown in FIG.10A. Notably, in FIG. 10A, top interconnect metal 982 (shown in FIG. 9A)has been patterned. As a result, heating element contacts 1086 areformed cross-wise to PCM contacts 1074. As used herein, “cross-wise”refers to the fact that PCM contacts 1074 are not situated in the samerow or in the same column as heating element contacts 1086.

Referring to FIG. 10B, PCM RF switch structure 1028B illustrates across-sectional view of a portion of a PCM RF switch structure processedin accordance with action 128 in flowchart 100B of FIG. 1B according toone implementation of the present application. FIG. 10B represents across-sectional view along line “B-B” in FIG. 10A. As shown in FIG. 10B,PCM RF switch structure 1028B includes substrate 1040, heat spreader1042, lower dielectric 1044, heating element 1046, nugget 1050, combinedlayer 1052, PCM 1054 having active segment 1056 and passive segments1058, contact dielectric 1060, PCM contacts 1074 having lower portions1066, upper portions 1070 with offset 1072, and top interconnect 1082,and interconnect dielectric 1076. Substrate 1040, heat spreader 1042,lower dielectric 1044, heating element 1046, nugget 1050, combined layer1052, PCM 1054 having active segment 1056 and passive segments 1058,contact dielectric 1060, PCM contacts 1074 having lower portions 1066,upper portions 1070 with offset 1072, and top interconnects 1083, andinterconnect dielectric 1076 in FIG. 10B may have any implementationsand advantages described above.

As shown in FIG. 10B, top interconnect metal 982 (shown in FIG. 9B) hasbeen patterned. As a result, top interconnects 1083 of PCM contacts 1074are formed. Top interconnects 1083 are connected to and substantiallyoverlie terminal segments of upper portions 1070 of PCM contacts 1074.

Referring to FIG. 10C, PCM RF switch structure 1028C illustrates across-sectional view of a portion of a PCM RF switch structure processedin accordance with action 128 in flowchart 100B of FIG. 1B according toone implementation of the present application. FIG. 10C represents across-sectional view along line “C-C” in FIG. 10A. As shown in FIG. 10C,PCM RF switch structure 1028C includes substrate 1040, heat spreader1042, lower dielectric 1044, heating element 1046, combined layer 1052,contact dielectric 1060, interconnect dielectric 1076, and heatingelement contact 1086. Substrate 1040, heat spreader 1042, lowerdielectric 1044, heating element 1046, combined layer 1052, contactdielectric 1060, and interconnect dielectric 1076 in FIG. 10C may haveany implementations and advantages described above.

As shown in FIG. 10C, top interconnect metal 982 (shown in FIG. 9C) hasbeen patterned. As a result, heating element contacts 1086 are formed.Heating element contacts 1086 are connected to and substantially overlieterminal segments of heating element 1046.

PCM RF switch structures 1028A, 1028B, and 1028C in FIGS. 10A, 10B, and10C represent a substantially complete PCM RF switch according to oneimplementation where flowchart 100A in FIG. 1A continues from action 116to action 118, and where upper portions 1070 of PCM contacts 1074 haveoffset 1072 towards active segment 1056 of PCM 1054. In anotherimplementation, flowchart 100A in FIG. 1A continues from action 116(corresponding to FIGS. 4A through 4C) to action 130 (corresponding toFIGS. 11A through 11C), and upper portions of PCM contacts will have anoffset away from the active segment of the PCM. FIGS. 11A through 14Cillustrate the results of performing actions 130 through 136 offlowchart 100A of FIG. 1A, according to one alternative implementationof the present disclosure. For example, structures 1130A, 11308, and1130C, show a PCM RF switch structure after performing action 130,structures 1232A, 1232B, and 1232C show a PCM RF switch structure afterperforming action 132, and so forth.

Referring to FIG. 11A, PCM RF switch structure 1130A illustrates a topview of a portion of a PCM RF switch structure processed in accordancewith action 130 in flowchart 100A of FIG. 1A according to oneimplementation of the present application. As shown in FIG. 11A, PCM RFswitch structure 1130A includes substrate 1140, heat spreader 1142,heating element 1146 having terminal segments 1148, PCM 1154 havingactive segment 1156, and lower portions 1167 of PCM contacts. Forpurposes of illustration, the top view in FIG. 11A shows selectedstructures of PCM RF switch structure 1130A. PCM RF switch structure1130A may include other structures not shown in FIG. 11A. Notably, inFIG. 11A, portions of lower interconnect metal 464 (shown in FIG. 4A)have been removed, leaving lower portions 1167 of PCM contacts in holes362 (shown in FIG. 3A) connected to passive segments of PCM 1154.

Referring to FIG. 11B, PCM RF switch structure 1130B illustrates across-sectional view of a portion of a PCM RF switch structure processedin accordance with action 130 in flowchart 100A of FIG. 1A according toone implementation of the present application. FIG. 11B represents across-sectional view along line “B-B” in FIG. 11A. As shown in FIG. 11B,PCM RF switch structure 1130B includes substrate 1140, heat spreader1142, lower dielectric 1144, heating element 1146, nugget 1150, combinedlayer 1152, PCM 1154 having active segment 1156 and passive segments1158, contact dielectric 1160, and lower portions 1167 of PCM contacts.Substrate 1140, heat spreader 1142, lower dielectric 1144, heatingelement 1146, nugget 1150, combined layer 1152, PCM 1154 having activesegment 1156 and passive segments 1158, and contact dielectric 1160 inFIG. 11B may have any implementations and advantages described above.

As shown in FIG. 11B, portions of lower interconnect metal 464 (shown inFIG. 4B) have been removed, thereby planarizing lower portions 1167 ofPCM contacts with contact dielectric 1160.

Referring to FIG. 11C, PCM RF switch structure 1130C illustrates across-sectional view of a portion of a PCM RF switch structure processedin accordance with action 130 in flowchart 100A of FIG. 1A according toone implementation of the present application. FIG. 11C represents across-sectional view along line “C-C” in FIG. 11A. As shown in FIG. 11C,PCM RF switch structure 1130C includes substrate 1140, heat spreader1142, lower dielectric 1144, heating element 1146, combined layer 1152,and contact dielectric 1160. Substrate 1140, heat spreader 1142, lowerdielectric 1144, heating element 1146, combined layer 1152, and contactdielectric 1160 in FIG. 11C may have any implementations and advantagesdescribed above. Notably, the cross-sectional view of PCM RF switchstructure 1130C in FIG. 11C does not include lower portions 1167 of PCMcontacts, because line “C-C” in FIG. 1 IA lies along terminal segment1148 of heating element 1146, which extends outward and is transverse toPCM 1154.

Referring to FIG. 12A, PCM RF switch structure 1232A illustrates a topview of a portion of a PCM RF switch structure processed in accordancewith action 132 in flowchart 100A of FIG. 1A according to oneimplementation of the present application. As shown in FIG. 12A, PCM RFswitch structure 1232A includes lower interconnect metal 1269. Forpurposes of illustration, the top view in FIG. 12A shows selectedstructures of PCM RF switch structure 1232A. PCM RF switch structure1232A may include other structures not shown in FIG. 12A. Notably, inFIG. 12A, lower interconnect metal 1269 is situated atop PCM RF switchstructure 1232A, but not in any holes, such as holes 362 (shown in FIG.3B).

Referring to FIG. 12B, PCM RF switch structure 1232B illustrates across-sectional view of a portion of a PCM RF switch structure processedin accordance with action 132 in flowchart 1100A of FIG. 1A according toone implementation of the present application. FIG. 12B represents across-sectional view along line “B-B” in FIG. 12A. As shown in FIG. 12B,PCM RF switch structure 1232B includes substrate 1240, heat spreader1242, lower dielectric 1244, heating element 1246, nugget 1250, combinedlayer 1252, PCM 1254 having active segment 1256 and passive segments1258, contact dielectric 1260, lower portions 1267 of PCM contacts, andlower interconnect metal 1269. Substrate 1240, heat spreader 1242, lowerdielectric 1244, heating element 1246, nugget 1250, combined layer 1252,PCM 1254 having active segment 1256 and passive segments 1258, contactdielectric 1260, and lower portions 1267 of PCM contacts in FIG. 12B mayhave any implementations and advantages described above.

As shown in FIG. 12B, lower interconnect metal 1269 is deposited overlower portions 1267 of PCM contacts and over contact dielectric 1260. Invarious implementations, lower interconnect metal 1269 can comprise W,Cu, or Al. In the present implementation, the top surface of lowerinterconnect metal 1269 has no indents or minimal indents in thevicinity of lower portions 1267 of PCM contacts, since lower portions1267 of PCM contacts are coplanar with contact dielectric 1260.

Referring to FIG. 12C, PCM RF switch structure 1232C illustrates across-sectional view of a portion of a PCM RF switch structure processedin accordance with action 132 in flowchart 100A of FIG. 1A according toone implementation of the present application. FIG. 12C represents across-sectional view along line “C-C” in FIG. 12A. As shown in FIG. 12C,PCM RF switch structure 1232C includes substrate 1240, heat spreader1242, lower dielectric 1244, heating element 1246, combined layer 1252,contact dielectric 1260, and lower interconnect metal 1269. Substrate1240, heat spreader 1242, lower dielectric 1244, heating element 1246,combined layer 1252, contact dielectric 1260 in FIG. 12C may have anyimplementations and advantages described above. Notably, thecross-sectional view of PCM RF switch structure 1232C in FIG. 12C doesnot include lower portions 1267 of PCM contacts, because line “C-C” inFIG. 12A lies along a terminal segment of heating element 1246, whichextends outward and is transverse to PCM 1254.

Referring to FIG. 13A, PCM RF switch structure 1334A illustrates a topview of a portion of a PCM RF switch structure processed in accordancewith action 134 in flowchart 100A of FIG. 1A according to oneimplementation of the present application. As shown in FIG. 13A, PCM RFswitch structure 1334A includes substrate 1340, heat spreader 1342,heating element 1346 having terminal segments 1348, PCM 1354 havingactive segment 1356, and PCM contacts 1375 having lower portions 1367and upper portions 1371. For purposes of illustration, the top view inFIG. 13A shows selected structures of PCM RF switch structure 1334A. PCMRF switch structure 1334A may include other structures not shown in FIG.13A. Notably, in FIG. 13A, upper portions 1371 of PCM contacts 1375 areformed from lower interconnect metal 1269 (shown in FIG. 12A).

Referring to FIG. 13B, PCM RF switch structure 1334B illustrates across-sectional view of a portion of a PCM RF switch structure processedin accordance with action 134 in flowchart 100A of FIG. 1A according toone implementation of the present application. FIG. 13B represents across-sectional view along line “B-B” in FIG. 13A. As shown in FIG. 13B,PCM RF switch structure 1334B includes substrate 1340, heat spreader1342, lower dielectric 1344, heating element 1346, nugget 1350, combinedlayer 1352, PCM 1354 having active segment 1356 and passive segments1358, contact dielectric 1360, and PCM contacts 1375 having lowerportions 1367 and upper portions 1371. Substrate 1340, heat spreader1342, lower dielectric 1344, heating element 1346, nugget 1350, combinedlayer 1352, PCM 1354 having active segment 1356 and passive segments1358, contact dielectric 1360, and lower portions 1367 of PCM contacts1375 in FIG. 13B may have any implementations and advantages describedabove.

As shown in FIG. 13B, lower interconnect metal 1269 (shown in FIG. 12B)has been patterned, thereby forming upper portions 1371 of PCM contacts1375. Because forming PCM contacts 1375 shown in FIG. 13B uses two metaldepositions, PCM contacts 1375 have lower portions 1367 connected topassive segments 1358 of PCM 1354 in holes 362 (shown in FIG. 3B), andhave upper portions 1371 having offsets 1373 away from active segment1356 of PCM 1354. Compared to offsets 572 in FIG. 5B, offsets 1373 inFIG. 13C reduce OFF state parasitic capacitance (C_(OFF)) between PCMcontacts 1375 due to the increased distance between PCM contacts 1375 oneach side of PCM 1354, thereby improving performance of PCM RF switchstructure 1334B. In one implementation, lower portions 1367 of PCMcontacts 1375 can comprise a different material than upper portions 1371of PCM contacts. For example, in one implementation, lower portions 1367of PCM contacts 1375 comprise a material that exhibits little orsubstantially no electromigration, while upper portions 1371 of PCMcontacts 1375 comprise a metal that can be patterned relatively easily.

Referring to FIG. 13C, PCM RF switch structure 1334C illustrates across-sectional view of a portion of a PCM RF switch structure processedin accordance with action 134 in flowchart 100A of FIG. 1A according toone implementation of the present application. FIG. 13C represents across-sectional view along line “C-C” in FIG. 13A. As shown in FIG. 13C,PCM RF switch structure 1334C includes substrate 1340, heat spreader1342, lower dielectric 1344, heating element 1346, combined layer 1352,and contact dielectric 1360. Substrate 1340, heat spreader 1342, lowerdielectric 1344, heating element 1346, combined layer 1352, and contactdielectric 1360 in FIG. 13C may have any implementations and advantagesdescribed above. Notably, the cross-sectional view of PCM RF switchstructure 1334C in FIG. 13C does not include PCM contacts 1375, becauseline “C-C” in FIG. 13A lies along terminal segment 1348 of heatingelement 1346, which extends outward and is transverse to PCM 1354.

Referring to FIGS. 14A, 14B, and 14C, PCM RF switch structures 1436A,1436B, and 1436C in FIGS. 14A, 14B, and 14C represent a substantiallycomplete PCM RF switch according to one implementation where upperportions 1471 of PCM contacts 1475 have offsets 1473 away from activesegment 1456 of PCM 1454, after performing action 136 of completingcontacts by remaining manufacturing actions. In this presentimplementation, the remaining manufacturing actions of action 136 areanalogous to actions 120 through 128, and therefore these remainingmanufacturing actions are not shown in detail. Only the substantiallycomplete PCM RF switch is shown in FIGS. 14A, 14B, and 14C.

Referring to FIG. 14A, PCM RF switch structure 1436A illustrates a topview of a portion of a PCM RF switch structure processed in accordancewith action 136 in flowchart 100A of FIG. 1A according to oneimplementation of the present application. As shown in FIG. 14A, PCM RFswitch structure 1436A includes substrate 1440, heat spreader 1442,heating element 1446, PCM 1454 having active segment 1456, PCM contacts1475 having lower portions 1467, upper portions 1471, and topinterconnects 1483, and heating element contacts 1486. For purposes ofillustration, the top view in FIG. 14A shows selected structures of PCMRF switch structure 1436A. PCM RF switch structure 1436A may includeother structures not shown in FIG. 14A. Notably, in FIG. 14A, topinterconnect metal has been patterned. As a result, heating elementcontacts 1486 are formed cross-wise to PCM contacts 1475. As usedherein, “cross-wise” refers to the fact that PCM contacts 1475 are notsituated in the same row or in the same column as heating elementcontacts 1486.

Referring to FIG. 14B, PCM RF switch structure 1436B illustrates across-sectional view of a portion of a PCM RF switch structure processedin accordance with action 136 according to one implementation of thepresent application. FIG. 14B represents a cross-sectional view alongline “B-B” in FIG. 14A. As shown in FIG. 14B, PCM RF switch structure1436B includes substrate 1440, heat spreader 1442, lower dielectric1444, heating element 1446, nugget 1450, combined layer 1452, PCM 1454having active segment 1456 and passive segments 1458, contact dielectric1460, PCM contacts 1475 having lower portions 1467, upper portions 1471with offset 1473, and top interconnects 1483, and interconnectdielectric 1476. Substrate 1440, heat spreader 1442, lower dielectric1444, heating element 1446, nugget 1450, combined layer 1452, PCM 1454having active segment 1456 and passive segments 1458, contact dielectric1460, PCM contacts 1475 having lower portions 1467, upper portions 1471with offset 1473, and top interconnects 1483, and interconnectdielectric 1476 in FIG. 14B may have any implementations and advantagesdescribed above.

As shown in FIG. 14B, top interconnect metal has been patterned. As aresult, top interconnects 1483 of PCM contacts 1475 are formed. Topinterconnects 1483 are connected to and substantially overlie terminalsegments of upper portions 1471 of PCM contacts 1475.

Referring to FIG. 14C, PCM RF switch structure 1436C illustrates across-sectional view of a portion of a PCM RF switch structure processedin accordance with action 136 in flowchart 100A of FIG. 1A according toone implementation of the present application. FIG. 14C represents across-sectional view along line “C-C” in FIG. 14A. As shown in FIG. 14C,PCM RF switch structure 1436C includes substrate 1440, heat spreader1442, lower dielectric 1444, heating element 1446, combined layer 1452,contact dielectric 1460, interconnect dielectric 1476, and heatingelement contact 1486. Substrate 1440, heat spreader 142, lowerdielectric 1444, heating element 1446, combined layer 1452, contactdielectric 1460, interconnect dielectric 1476, and heating elementcontact 1486 in FIG. 14C may have any implementations and advantagesdescribed above.

As shown in FIG. 14C, top interconnect metal has been patterned. As aresult, heating element contacts 1486 are formed. Heating elementcontacts 1486 are connected to and substantially overlie terminalsegments of heating element 1446.

Referring to FIG. 15, PCM RF switch structure 1500 illustrates across-sectional view of a portion of a PCM RF switch structure accordingto one implementation of the present application. FIG. 15 represents across-sectional view along line “C-C” in FIG. 10A or 14A for analternative implementation where the top interconnect metal does notdirectly connect to the heating element. As shown in FIG. 15, PCM RFswitch structure 1500 includes substrate 1540, heat spreader 1542, lowerdielectric 1544, heating element 1546, combined layer 1552, contactdielectric 1560, interconnect dielectric 1576, and heating elementcontact 1586 having top interconnect 1583 and intermediate metalsegments 1588 a and 1588 b. Substrate 1540, heat spreader 1542, lowerdielectric 1544, heating element 1546, combined layer 1552, contactdielectric 1560, interconnect dielectric 1576, and top interconnect 1583in FIG. 15 may have any implementations and advantages described above.

As shown in FIG. 15, heating element contact 1586 includes topinterconnect 1583 and intermediate metal segments 1588 a and 1588 b.Intermediate metal segment 1588 a is situated on heating element 1546,extends through lower dielectric 1544, combined layer 1552 (in casecombined layer 1552 is utilized), and contact dielectric 1560, andconnects to intermediate metal segment 1588 b. Intermediate metalsegment 1588 b is situated on intermediate metal segment 1588 a andcontact dielectric 1560, extends partially through interconnectdielectric 1576, and connects to top interconnect 1583. Top interconnect1583 is situated on intermediate metal segment 1588 b and interconnectdielectric 1576. In various implementations, heating element contact1586 can include more or fewer intermediate metal segments havingdifferent sizes or shapes and situated on or extending through differentlayers. In various implementations, intermediate metal segments areformed overlying terminal segments of lower active structures away froman active segment of PCM.

By utilizing the methods disclosed in the present application, contactsfor an RF switch employing phase-change material, such as PCM 1054 inFIGS. 10A and 10B, can be reliably manufactured. Lower portions 1066 ofPCM contacts 1074 connect to passive segments 1058 of PCM 1054 thatextend outward and are transverse to heating element 1046, reducingparasitic capacitance between PCM contacts 1074 and heating element1046, and reducing C_(OFF) of PCM RF switch 1028A/1028B. Because lowerportions 1066 of PCM contacts 1074 connect to passive segments 1058 ofPCM 1054, lower portions 1066 of PCM contacts 1074 are also subject toless thermal cycling and thus, less variation in R_(ON), and lesspossibility of damage. Using contact uniformity support layer incombined layer 1052 over PCM 1054 as an etch stop during formation oflower portions 1066 of PCM contacts 1074 advantageously reduces R_(ON).PCM contacts 1074 with upper portions 1070 having offsets 1072 towardsactive segment 1056 of PCM 1054 can reduce manufacturing complexity.Meanwhile, in the alternative implementation and referring to FIGS. 14Aand 14B, PCM contacts 1475 with upper portions 1471 having offsets 1473away from active segment 1456 of PCM 1454 reduce parasitic capacitancebetween PCM contacts 1475, reducing C_(OFF) of PCM RF switch 1436B.

In a departure from conventional contact formation, holes 362 (shown inFIG. 3B) in contact dielectric 1060 overlying passive segments 1058 ofPCM 1054, and holes 778 (shown in FIG. 7B) in interconnect dielectric1076 overlying terminal segments of upper portions 1070 of PCM contacts1074, can each be formed separately from holes 880 (shown in FIG. 8C) ininterconnect dielectric 1076 and contact dielectric 1060 overlyingterminal segments of heating element 1046. Top interconnect metal 982(shown in FIGS. 9B and 9C) can be deposited to different depths, andthus, can be patterned to form both top interconnects 1083 of PCMcontacts 1074 and heating element contacts 1086 directly connected toheating element 1046, which underlies PCM 1054.

Finally, heating element contacts 1086 are formed cross-wise to PCMcontacts 1074, and metal layers thereof are formed overlying terminalsegments of lower active structures away from active segment 1056 of PCM1054. Thus, PCM contacts 1074 and heating element contacts 1086 haveeffectively increased separation. Because larger contacts are necessaryto efficiently operate a switch, but detrimentally increase RF parasiticcapacitance, this increased separation significantly reduces parasiticcapacitance between PCM contacts 1074 and heating element contacts 1086,reducing C_(OFF) of PCM RF switch 1028A.

Thus, various implementations of the present application achieve amethod of manufacturing a PCM RF switch that overcomes the deficienciesin the art. From the above description it is manifest that varioustechniques can be used for implementing the concepts described in thepresent application without departing from the scope of those concepts.Moreover, while the concepts have been described with specific referenceto certain implementations, a person of ordinary skill in the art wouldrecognize that changes can be made in form and detail without departingfrom the scope of those concepts. As such, the described implementationsare to be considered in all respects as illustrative and notrestrictive. It should also be understood that the present applicationis not limited to the particular implementations described above, butmany rearrangements, modifications, and substitutions are possiblewithout departing from the scope of the present disclosure.

The invention claimed is:
 1. A radio frequency (RF) switch comprising: aphase-change material (PCM) and a heating element approximatelyunderlying an active segment of said PCM and extending outward andtransverse to said PCM; PCM contacts comprising lower portions and upperportions; said lower portions of said PCM contacts connected to passivesegments of said PCM, wherein said passive segments extend outward andare transverse to said heating element; said upper portions of said PCMcontacts made from a lower interconnect metal, wherein said upperportions of said PCM contacts have an offset away from said activesegment of said PCM; heating element contacts comprising a topinterconnect metal and intermediate metal segments for connecting withterminal segments of said heating element; said heating element contactsbeing situated cross-wise to said PCM contacts so as to reduce a C_(OFF)of said PCM.
 2. The radio frequency (RF) switch of claim 1, furthercomprising a contact uniformity support layer over said PCM.
 3. Theradio frequency (RF) switch of claim 1, further including a nuggetcomprising a thermally conductive and electrically insulating materialsituated on top of said heating element.
 4. The radio frequency (RF)switch of claim 3, wherein said thermally conductive and electricallyinsulating material is selected from the group consisting of AlN,Al_(X)O_(Y), Be_(X)O_(Y), SiC, Si_(X)N_(Y), diamond, and diamond-likecarbon.
 5. The radio frequency (RF) switch of claim 1, wherein saidlower portions of said PCM contacts are formed from said lowerinterconnect metal.
 6. The radio frequency (RF) switch of claim 1,wherein said lower portions of said PCM contacts are planarized with acontact dielectric.
 7. The radio frequency (RF) switch of claim 1,wherein said PCM comprises a material selected from the group consistingof germanium telluride (Ge_(X)Te_(Y)), germanium antimony telluride(Ge_(X)Sb_(Y)Te_(Z)), germanium selenide (Ge_(X)Se_(Y)), and any otherchalcogenide.
 8. A radio frequency (RF) switch comprising: aphase-change material (PCM) and a heating element approximatelyunderlying an active segment of said PCM; a PCM contact comprising alower portion and an upper portion; said lower portion of said PCMcontact connected to a passive segment of said PCM; said upper portionof said PCM contact having an offset away from said active segment ofsaid PCM; a heating element contact comprising a top interconnect metaland intermediate metal segments for connecting with a terminal segmentof said heating element.
 9. The radio frequency (RF) switch of claim 8,wherein said upper portion of said PCM contact is made from a lowerinterconnect metal.
 10. The radio frequency (RF) switch of claim 9,wherein said lower portion of said PCM contact is formed from said lowerinterconnect metal.
 11. The radio frequency (RF) switch of claim 8,wherein said lower portion of said PCM contact is planarized with acontact dielectric.
 12. The radio frequency (RF) switch of claim 8further comprising a contact uniformity support layer over said PCM. 13.The radio frequency (RF) switch of claim 8 further including a nuggetcomprising a thermally conductive and electrically insulating materialsituated on top of said heating element.
 14. The radio frequency (RF)switch of claim 13, wherein said thermally conductive and electricallyinsulating material is selected from the group consisting of AlN,Al_(X)O_(Y), Be_(X)O_(Y), SiC, Si_(X)N_(Y), diamond, and diamond-likecarbon.
 15. The radio frequency (RF) switch of claim 8, wherein said PCMcomprises a material selected from the group consisting of germaniumtelluride (Ge_(X)Te_(Y)), germanium antimony telluride(Ge_(X)Sb_(Y)Te_(Z)), germanium selenide (Ge_(X)Se_(Y)), and any otherchalcogenide.
 16. A radio frequency (RF) switch comprising: aphase-change material (PCM) and a heating element approximatelyunderlying an active segment of said PCM and extending outward andtransverse to said PCM; a thermally conductive and electricallyinsulating material situated over said heating element; PCM contactscomprising lower portions and upper portions; said lower portions ofsaid PCM contacts connected to passive segments of said PCM, whereinsaid passive segments extend outward and are transverse to said heatingelement; said upper portions of said PCM contacts made from a lowerinterconnect metal wherein said upper portions of said PCM contacts havean offset away from said active segment of said PCM; heating elementcontacts comprising a top interconnect metal and intermediate metalsegments for connecting with terminal segments of said heating element.17. The radio frequency (RF) switch of claim 16 further comprising acontact uniformity support layer over said PCM.
 18. The radio frequency(RF) switch of claim 16, wherein said thermally conductive andelectrically insulating material is selected from the group consistingof AlN, Al_(X)O_(Y), Be_(X)O_(Y), SiC, Si_(X)N_(Y), diamond, anddiamond-like carbon.
 19. The radio frequency (RF) switch of claim 16,wherein said PCM comprises a material selected from the group consistingof germanium telluride (Ge_(X)Te_(Y)), germanium antimony telluride(Ge_(X)Sb_(Y)Te_(Z)), germanium selenide (Ge_(X)Se_(Y)), and any otherchalcogenide.
 20. The radio frequency (RF) switch of claim 16, whereinsaid thermally conductive and electrically insulating material isselected from the group consisting of AlN, Al_(X)O_(Y), Be_(X)O_(Y),SiC, Si_(X)N_(Y), diamond, and diamond-like carbon, and wherein said PCMcomprises a material selected from the group consisting of germaniumtelluride (Ge_(X)Te_(Y)), germanium antimony telluride(Ge_(X)Sb_(Y)Te_(Z)), germanium selenide (Ge_(X)Se_(Y)), and any otherchalcogenide.